(a) Field of the Invention
The present invention relates to a vacuum fluorescent display and, more particularly, to a vacuum fluorescent display which can effectively increase the area of displaying images.
(b) Description of the Related Art
Vacuum fluorescent displays are display devices where electrons are liberated from the cathode and strike phosphors coated on the anode to create display images. Such a vacuum fluorescent display is capable of producing multi-colored images with a low voltage, and is well adapted to the semiconductor device appliances. Therefore, the vacuum fluorescent displays are attracted for various display purposes.
FIG. 6 is an exploded perspective view of a vacuum fluorescent display according to a prior art, FIG. 7 is a plan view of the vacuum fluorescent display shown in FIG. 6, and FIG. 8 is a sectional view of the vacuum fluorescent display taken along the Fxe2x80x94F line of FIG. 7.
As shown in the drawings, the vacuum fluorescent display includes a transparent front glass substrate 2, a rear glass substrate 4 spaced apart from the front glass substrate 2 with a predetermined distance, and a side glass 3 interposed between the front glass substrate 2 and the rear glass substrate 4 while forming an inner vacuum space for receiving electrode components. The front glass substrate 2 and the rear glass substrate 4 are rectangular-shaped each with two long sides and two short sides.
A plurality of anode electrodes 8 are arranged on the rear glass substrate 4 in a predetermined pattern, and coated with phosphors. The display area D corresponds to the pattern of the anode electrodes 8.
A plurality of grids 7 are mounted above the anode electrodes 8, and a plurality of filaments 6 are placed above the grids 7 to function as electron-emitting cathode electrodes. Each of the grids 7 has side bent portions, and the side bent portions of the grid 7 are fixed to the rear glass substrate 4 such that the grid 7 can be spaced apart from the anode electrodes 8 with a predetermined distance. A plurality of leads 9 are fixed onto one of the long sides of the rear glass substrate 4 to apply voltages to the grids 7 and the anode electrodes 8.
Each of the filaments 6 has two ends, and the ends of each filament 6 are fixed to supports 10 on the rear glass substrate 4, respectively. The supports 10 are fixed onto both of the short sides of the rear glass substrate 4. In this structure, the filaments 6 are arranged to be perpendicular to the leads 9.
The filaments 6 are welded to the supports 10 at welding points. In operation, the side portions of each filament 6 sustain thermal loss through the welding points. Therefore, the side portions of the filament 6 close to the welding points do not emit sufficient amount of thermal electrons for exciting the phosphors on the anode electrodes 8. The area C corresponding to such side portions of the filament 6 is usually referred to as the xe2x80x9cend cooling zonexe2x80x9d.
In the above-structured vacuum fluorescent display, the leads 9 and the supports 10 for supporting the filaments 6 are oriented at the sides of the rear glass substrate 4 different in direction so that the end cooling zones C are present in relatively large areas over the display device. This means that the display area D of the vacuum fluorescent display decreases as much.
It is an object of the present invention to provide a vacuum fluorescent display which increases the display area while minimizing the end cooling zones.
These and other objects may be achieved by a vacuum fluorescent display including first and second substrates spaced apart from each other with a predetermined distance. Each substrate has lateral sides in horizontal and vertical directions. A plurality of anode electrodes are arranged on the second substrate in a predetermined pattern. The anode electrodes are coated with phosphors. A plurality of filaments are mounted above the anode electrodes to emit thermal electrons for exciting the phosphors. A plurality of leads are arranged on one of the opposite lateral sides of the second substrate in one of the horizontal and vertical directions to apply voltages to the anode electrodes. Supports are arranged on both of the opposite sides of the second substrate in the direction of arrangement of the leads to support the filaments.